KeyDerivationExtensions

Namespace: WvdS.System.Security.Cryptography.KeyDerivation

Statische Klasse für Schlüsselableitung (Key Derivation Functions) mit Post-Quantum Support. Unterstützt HKDF, PBKDF2 und Argon2id.

Unterstützte KDF-Algorithmen:

Leitet Schlüssel aus einem Shared Secret ab (HKDF-Extract-then-Expand).

// ML-KEM Shared Secret aus Key Exchange
byte[] sharedSecret = session.SharedSecret;
 
// Standard-Ableitung (SHA-256)
byte[] aesKey = KeyDerivationExtensions.DeriveKey(
    sharedSecret,
    outputLength: 32);  // 256 Bit
 
// Mit Salt und Context-Info
byte[] salt = RandomNumberGenerator.GetBytes(32);
byte[] info = Encoding.UTF8.GetBytes("MyApp-Session-Key");
 
byte[] sessionKey = KeyDerivationExtensions.DeriveKey(
    sharedSecret,
    outputLength: 32,
    salt: salt,
    info: info,
    hashAlgorithm: HashAlgorithmName.SHA384);  // Optional

Extrahiert PRK (Pseudorandom Key) aus Input Key Material.

byte[] inputKeyMaterial = GetSharedSecret();
byte[] salt = RandomNumberGenerator.GetBytes(32);
 
byte[] prk = KeyDerivationExtensions.HkdfExtract(
    inputKeyMaterial,
    salt: salt,
    hashAlgorithm: HashAlgorithmName.SHA256);
 
// PRK hat gleiche Länge wie Hash-Output (32 Bytes bei SHA-256)

Expandiert PRK zu Output Key Material.

byte[] prk = GetPrk();
 
// Encryption Key
byte[] encKey = KeyDerivationExtensions.HkdfExpand(
    prk,
    outputLength: 32,
    info: Encoding.UTF8.GetBytes("encryption"));
 
// MAC Key
byte[] macKey = KeyDerivationExtensions.HkdfExpand(
    prk,
    outputLength: 32,
    info: Encoding.UTF8.GetBytes("mac"));

Kombiniert klassische (ECDH/DH) und PQ (ML-KEM) Shared Secrets.

byte[] ecdhSecret = GetEcdhSharedSecret();
byte[] mlKemSecret = GetMlKemSharedSecret();
 
// Hybrid-Modus: Beide Secrets werden kombiniert
byte[] hybridKey = KeyDerivationExtensions.DeriveHybridKey(
    classicSecret: ecdhSecret,
    pqSecret: mlKemSecret,
    outputLength: 32,
    mode: CryptoMode.Hybrid);
 
// Nur klassisch
byte[] classicKey = KeyDerivationExtensions.DeriveHybridKey(
    classicSecret: ecdhSecret,
    pqSecret: null,
    outputLength: 32,
    mode: CryptoMode.Classic);
 
// Nur Post-Quantum
byte[] pqKey = KeyDerivationExtensions.DeriveHybridKey(
    classicSecret: null,
    pqSecret: mlKemSecret,
    outputLength: 32,
    mode: CryptoMode.PostQuantum);
 
// Custom Info
byte[] customKey = KeyDerivationExtensions.DeriveHybridKey(
    classicSecret: ecdhSecret,
    pqSecret: mlKemSecret,
    outputLength: 64,
    mode: CryptoMode.Hybrid,
    info: Encoding.UTF8.GetBytes("MyProtocol-v1"));

Schlüssel-Kombination:

Hybrid Mode:
  IKM = classicSecret || pqSecret
  Key = HKDF-SHA256(IKM, info="WvdS-Hybrid-Key")

Leitet mehrere Schlüssel für verschiedene Zwecke ab.

using HybridKeyMaterial keyMaterial = KeyDerivationExtensions.DeriveHybridKeyMaterial(
    classicSecret: ecdhSecret,
    pqSecret: mlKemSecret,
    mode: CryptoMode.Hybrid);
 
// Verwendung
byte[] encKey = keyMaterial.EncryptionKey;  // 32 Bytes
byte[] macKey = keyMaterial.MacKey;         // 32 Bytes
byte[] iv = keyMaterial.Iv;                 // 16 Bytes
byte[] authKey = keyMaterial.AuthKey;       // 32 Bytes
 
// IDisposable: Schlüssel werden sicher gelöscht

string password = "SecurePassword123!";
byte[] salt = RandomNumberGenerator.GetBytes(32);
 
// Standard PBKDF2
byte[] key = KeyDerivationExtensions.Pbkdf2(
    password,
    salt,
    iterations: 100000,
    outputLength: 32);
 
// Mit PQ-Entropy (zusätzlicher Schutz)
byte[] pqEntropy = GetPqEntropy();
 
byte[] enhancedKey = KeyDerivationExtensions.Pbkdf2(
    password,
    salt,
    iterations: 100000,
    outputLength: 32,
    pqEntropy: pqEntropy,  // Wird mit Salt kombiniert
    hashAlgorithm: HashAlgorithmName.SHA512);

PBKDF2 mit PQ-verstärktem Salt (Public Key wird in Salt-Berechnung einbezogen).

string password = "UserPassword";
byte[] baseSalt = RandomNumberGenerator.GetBytes(16);
byte[] mlKemPublicKey = GetRecipientPublicKey();
 
// Salt = SHA256(baseSalt || pqPublicKey)
byte[] key = KeyDerivationExtensions.Pbkdf2WithPqSalt(
    password,
    baseSalt,
    mlKemPublicKey,
    iterations: 100000,
    outputLength: 32);

Argon2id via OpenSSL 3.6 - widerstandsfähig gegen GPU/ASIC-Angriffe.

byte[] password = Encoding.UTF8.GetBytes("SecurePassword");
byte[] salt = RandomNumberGenerator.GetBytes(16);  // Mindestens 16 Bytes
 
byte[] key = KeyDerivationExtensions.Argon2id(
    password,
    salt,
    outputLength: 32,     // Key-Länge
    iterations: 3,        // Zeit-Kosten (t)
    memoryKiB: 65536,     // Speicher: 64 MB
    parallelism: 4);      // Threads (p)

string password = "UserPassword123";
byte[] salt = RandomNumberGenerator.GetBytes(16);
 
byte[] key = KeyDerivationExtensions.Argon2id(
    password,
    salt,
    outputLength: 32,
    iterations: 3,
    memoryKiB: 65536,
    parallelism: 4);

Empfohlene Parameter:

byte[] preMasterSecret = GetPreMasterSecret();
byte[] clientRandom = GetClientRandom();
byte[] serverRandom = GetServerRandom();
 
using TlsKeyMaterial keys = KeyDerivationExtensions.DeriveTlsKeys(
    preMasterSecret,
    clientRandom,
    serverRandom,
    mode: CryptoMode.Hybrid);
 
// Verwendung
var clientKey = keys.ClientWriteKey;   // 32 Bytes
var serverKey = keys.ServerWriteKey;   // 32 Bytes
var clientIv = keys.ClientWriteIv;     // 12 Bytes
var serverIv = keys.ServerWriteIv;     // 12 Bytes

TLS 1.3 kompatible Key Schedule.

byte[]? pskSecret = null;  // Pre-Shared Key (optional)
byte[] ecdhSecret = GetEcdhSecret();
byte[] pqSecret = GetMlKemSecret();
byte[] clientHello = GetClientHelloBytes();
byte[] serverHello = GetServerHelloBytes();
 
using Tls13KeySchedule schedule = KeyDerivationExtensions.DeriveTls13Keys(
    pskSecret,
    ecdhSecret,
    pqSecret,
    clientHello,
    serverHello,
    mode: CryptoMode.Hybrid);
 
// Handshake Traffic Secrets
var clientHsSecret = schedule.ClientHandshakeTrafficSecret;
var serverHsSecret = schedule.ServerHandshakeTrafficSecret;
 
// Application Traffic Secrets
var clientAppSecret = schedule.ClientApplicationTrafficSecret;
var serverAppSecret = schedule.ServerApplicationTrafficSecret;
 
// Resumption Secret
var resumptionSecret = schedule.ResumptionMasterSecret;

Container für abgeleitete Schlüssel mit sicherer Speicherbereinigung.

using HybridKeyMaterial keys = DeriveKeys();
 
// Keys werden bei Dispose() sicher gelöscht
// (CryptographicOperations.ZeroMemory)

TLS 1.2 Style Schlüsselmaterial.

TLS 1.3 Key Schedule.

using WvdS.System.Security.Cryptography;
using WvdS.System.Security.Cryptography.KeyDerivation;
using WvdS.System.Security.Cryptography.KeyExchange;
 
// 1. Key Exchange durchführen
using var session = new KeyExchangeService();
await session.InitiateKeyExchangeAsync(recipientPublicKey, CryptoMode.Hybrid);
 
// 2. Hybrid Key Material ableiten
using HybridKeyMaterial keys = KeyDerivationExtensions.DeriveHybridKeyMaterial(
    classicSecret: session.ClassicSharedSecret,
    pqSecret: session.PqSharedSecret,
    mode: CryptoMode.Hybrid);
 
// 3. Schlüssel verwenden
using var aes = Aes.Create();
aes.Key = keys.EncryptionKey;
 
using var hmac = new HMACSHA256(keys.MacKey);
 
// 4. Verschlüsselung durchführen
// ...
 
// 5. Schlüssel werden automatisch sicher gelöscht

• KeyDerivation Namespace
• HybridKeyMaterial
• TlsKeyMaterial
• Tls13KeySchedule
• KeyExchange Namespace
• Encryption Namespace
• ML-KEM Algorithmus

Wolfgang van der Stille @ EMSR DATA d.o.o. - Post-Quantum Cryptography Professional